In order to understand how vertebrate peripheral sensory systems are formed during embryogenesis, it is necessary to understand how the various components of these systems develop. In all vertebrates, epibranchial placodes, along with the neural crest, contribute to the formation of sensory ganglia of the facial, glosso-pharyngeal and vagal cranial nerves which innervate taste buds. However, in contrast to neural crest, little is known about the development of epibranchial placodes. This proposal is designed to investigate the embryonic origins, induction and axial patterning of these placodes. The specific aims of this proposal are 1. to determine the embryonic source of epibranchial placodes; 2. to identify the tissue(s) that iduce epibranchial placodes to form and; 3. to examine the possible role of Hox genes in the axial patterning of these placodes. These questions will be addressed using salamander embryos which are uniquely appropriate for these studies. Embryonic transplantations of presumptive placodal tissue at precise stages will be used to discern the embryonic source (aim 1) and possible inducers (aim 2) of epibranchial placodes while in situ hybridizations will be used to determine whether Hox genes may be involved in the patterning of these placodes (aim 3).